A device is known for providing an optimum body posture (ref. Patent RU No. 21 70 539, Class A47C 7/40, A61F 5/34, published on Jul. 20, 2001) that comprises a supporting member of a curvilinear convex shape intended to support the back and to avoid cyphosing of the lumbar spine. The supporting member consists of two layers, either of a symmetrical shape, or in the shape of an aircraft wing, with deflection depth in horizontal cross section ranging from 0 to 50 cm, and with the layer stiffness ratio ranging from 1:1.2 to 1:3.
As regards disadvantages of this device, during operation, activity balance is disturbed of the functional element of the vertebral column, such as muscles, ligaments, and joints, since long fixation of individual functional elements causes their activity reduction, and increases activity of the elements located above the fixation point. Another disadvantage is the static character of the device structure, so that its application for a long time causes hypodynamia.
A device is known for prevention of the human spinal curvature and for training the back muscles in sedentary position (ref. Patent RTJ No. 22.76 571, Class A47C 7/02, A61H 1/00, A63B 23/02, published on May 20, 2006) by means of using a balancing removable seat. The seat comprises a balancing member and a support, whereupon a stand with a pivot is fixed. The pivot links the support with the balancing member.
As regards disadvantages of this device, it is unable to provide the necessary position for the vertebral column, since removable seats modify the structural parameter ratio between the back and the chair, which affects the vertebra support. Another disadvantage is the fact that the seat has no static and comfortable positions, whereby application of this device is limited.
A device is known for providing an optimum human body posture in sedentary position (ref. Patent RU No 21 59 568, Class A47C 1/02, 7/50, published on Nov. 27, 2000) by means of using a knee rest. This device has been used as a prototype for the variants of the chair of the present invention. The arm chair called ‘Zdorovie’ comprises a base whereupon a telescopic stand is fixed. It is provided with a calf rest with adjustable height, tilt and distance to the seat. The seat features a supporting mechanism for tilt angle adjustment, which comprises a handle and a rest tilted to 20°; it is installed with the center of gravity shifted forward. The base consists of two axes and a cross member that links the center of the front axis with the top of the telescopic stand, and its bottom with the center of the rear axis. Both the axes are provided with roller supports.
As regards disadvantages of this device, it is unable to provide the necessary position for the vertebral column, since there is no back rest. Another disadvantage is the static character of the device' structure, so that its application for a long time causes hypodynamia.